There was another knock at the door. This time it was four students, and they were easier to convince than the teachers had been. I asked one of them to go and make a sign for the door, saying that the cafeteria was closed because of a possible contamination. Which was true, in a way.
When I stepped back into the room, my employer was saying, "I'd like to focus now on two big questions. Either this was an attempt to poison a specific person, or it was a random act of malice, directed against whoever happened to drink from that cup. And, either the cup was poisoned before it was handed to Pete, or after he put it down. I was looking at Pete during the moment it was in his hand, and I can say with confidence that he didn't have the opportunity to poison it himself."
James raised his hand, as if he was in class, and Jan smiled and nodded.
"Would somebody really poison a cup of soda that was just sitting on a table?" he asked. "What if nobody came along and drank it?"
"Those things do happen, but I agree that they don't usually happen in this way. If it was a random act of malice, why was it so focused? Several of us drank soda, and none of us suffered any ill effects. Except by accident, we might never have even found out that the soda in that particular cup had been poisoned. If it was motiveless malignancy, I think it would have been broader, with more of the cups poisoned.
"So, let's take that as a hypothesis, and see where it takes us. Let's say it was an attempt to poison Pete, thwarted only by the fact that he doesn't drink soda. Did anybody here know Pete before today?"
Nobody said anything, then Willy said, "I've seen him around, here and there, in different bars. I don't think I ever said anything to him."
"Pete, did you know anybody here before today?"